In order to improve the safety or convenience of automobiles, systems, such as a pre-crash safety system (PCS) and a radar cruise control system (RCC), have been developed or put into production. Various systems, such as a system which performs control such that a host vehicle autonomously travels on a road to a destination while automatically avoiding obstacles and a system which provides a driver with notification of the approach of obstacles or the obstacle avoidance directions, have been suggested. For this reason, a technique which enables the recognition of information relating to obstacles, such as other vehicles which are traveling around the host vehicle, with satisfactory precision has become important.
For example, Patent Literature 1 describes a device which monitors the head portion or eye line of a driver of a vehicle, directs a sensor head portion to the line of sight of the driver, and detects vehicles, obstacles, and the like in a direction to which the driver pays attention, making it possible to cope with an unexpected event.